Under the IEEE Standard 802.11, wireless stations (STA) and access points (AP) may operate in an infrastructure mode. Infrastructure mode defines a set of communication protocols, one of which is an association protocol for a station to join an access point, another of which provides for an access point which operates continuously to periodically communicate with a station which has the characteristic of being in a power-down (sleep) mode, where the station periodically is activated into a power-up (wake-up) state to receive a Delivery Traffic Indication Map (DTIM) which indicates whether there are packets to be transmitted to the newly-awakened station. This power-saver protocol conserves a significant amount of power by only consuming power when in the power-up state (the interval when power is applied to the receiver circuits) shortly prior to the expected arrival of a beacon frame, and where the power-up state occurs during defined intervals related to periodic beacon intervals. In one example prior art embodiment, the wireless AP transmits a frame known as Delivery Traffic Indication Map (DTIM) and the STA responds indicating how often the station will wakeup to check the beacon frame to receive or transmit to the AP. According to the 802.11 power-saver protocol for stations, the station is in a power-up state shortly prior to the expected arrival of the AP beacon frame, and the STA stays powered on long enough during this interval to determine whether the traffic map of the beacon frame indicates there are receive packets destined to the AP, and if so, the station STA remains in a power-up state until the packets are received.
A problem arises in congested networks, where the STA may wake up at the appointed beacon interval, but the beacon frame is delayed in transmission because of network congestion (such as from an associated station transmitting, or a station or other access point on the same WLAN channel is nearby and interfering), in which case the AP waits for a clear channel before transmitting. During either of these disruptions, the STA remains powered up and awaiting reception of the delayed WLAN beacon frame, causing unwanted power consumption. It is desired to provide a power saving apparatus and method which provides improved power savings in a station operative in congested networks where the station wakes up and the expected beacon is delayed because of network congestion or interferers.